Highbeams issue

Discussion in 'Technical' started by Jim1969pa3, Oct 31, 2013.

  1. Jim1969pa3

    Jim1969pa3 Member

    Joined:
    Feb 25, 2013
    Messages:
    29
    Likes Received:
    0
    Trophy Points:
    0
    Vehicle:
    77 Maverick 4 door
    Well, I finally got this thing on the road! Thank you all for your valued input.

    I am having an issue with the high beams that I can't figure out.

    When the high beam switch is hit nothing happens. According to the light in the dash the high beams are on. All the time.

    I tested the switch. And I think it is operating as it should. Common to one post connected, then common to the other. I have a wiring diagram that someone was so gracious to provide me on here, and it looks like the high and low beams are pretty much connected to the posts like I would have figured, light-green/black to one side (High Beam), and red/black low beam.

    On the diagram I have, the light-green/black runs back to the "printed circuit connector". But I do not see the high beam indicator light anywhere.
     
  2. Bryant

    Bryant forgot more than learned

    Joined:
    Aug 7, 2007
    Messages:
    6,538
    Likes Received:
    153
    Trophy Points:
    203
    Garage:
    1
    Location:
    San Diego
    Vehicle:
    71 Maverick
    check the grounds for the head lights. if one has a bad ground it will back feed though the bright circuit
     
  3. 71gold

    71gold Frank Cooper Supporting Member

    Joined:
    Apr 9, 2002
    Messages:
    26,590
    Likes Received:
    2,935
    Trophy Points:
    978
    Garage:
    1
    Location:
    MACON,GA.
    Vehicle:
    '73 Grabber
    seems to always be a...no good ground...:yup:
     
  4. rthomas771

    rthomas771 Member

    Joined:
    Jan 22, 2008
    Messages:
    8,080
    Likes Received:
    969
    Trophy Points:
    498
    Garage:
    1
    Location:
    GA
    Vehicle:
    '74 Maverick 302 5-Speed.'60 Falcon V8. '63.5 Falcon HT
    Could also be a burned out filaments.
     
  5. Jim1969pa3

    Jim1969pa3 Member

    Joined:
    Feb 25, 2013
    Messages:
    29
    Likes Received:
    0
    Trophy Points:
    0
    Vehicle:
    77 Maverick 4 door
    Ok here's the skinny. I tested the ground (resistance) and it was less than an ohm from the ground in the harness to the negative battery terminal. I tested the filaments, and, at least on the one I headlight pulled I had about .7 Ohms. I am assuming that both high and low on that side is good.

    The peculiar thing is that with the headlights on I am measuring 10.7V on the highbeam post. Of course there is no difference if I hit the switch or not. So I have a voltage drop somewhere. And I was getting negligible if any voltage from the low beam terminal.

    My first guess was back to the bad ground again. So I tested both from the ground in the harness to the high beam terminal, and directly on the negative terminal on the battery. Both were 10.7V to the high beam wire.
    I measured across all of the fuses to see if I had a bad connection causing a resistance, and a voltage drop. I couldn't find this 2 volts anywhere. (the battery was reading 12.8V).
     
    Last edited: Nov 1, 2013
  6. Jim1969pa3

    Jim1969pa3 Member

    Joined:
    Feb 25, 2013
    Messages:
    29
    Likes Received:
    0
    Trophy Points:
    0
    Vehicle:
    77 Maverick 4 door
    Maybe there is some other ground for the instrument panel that may have been missed when we swapped the engine? It looks like the ground for the headlights is connected to the body just below the lights. Maybe I am looking for a ground for this "printed circuit"?

    I did just re-read all of the posts. I did not check the ground on the right headlight yet. I will do that soon.
     
    Last edited: Nov 1, 2013
  7. Krazy Comet

    Krazy Comet Tom

    Joined:
    Sep 13, 2012
    Messages:
    7,732
    Likes Received:
    2,441
    Trophy Points:
    531
    Garage:
    1
    Location:
    Chesapeake VA
    Vehicle:
    1972 Comet GT clone 306 . 1969 Fairlane Cobra 428CJ 1988 T-Bird awaiting 331 ..

    Assuming power & not ground is switched by the dimmer, could well be a bad switch and you are reading a "ghost voltage"(after all Halloween is over and they have nothing better to do) :hide:

    Check voltage at headlight plug with light in place, or use a test light I'm guessing with load voltage will disappear...
     
  8. Jim1969pa3

    Jim1969pa3 Member

    Joined:
    Feb 25, 2013
    Messages:
    29
    Likes Received:
    0
    Trophy Points:
    0
    Vehicle:
    77 Maverick 4 door
    OK speaking of ghosts we did have a visit apparently. And I guess it was divine. For some unexplained reason it just started working. I have no explanation...
     

Share This Page